Hi all, Would any one on here know what the black round quite high necked garment that seems to be under the gown and kirtle is in these images? I was wondering if it was a chemise of some sort. What are everyone else’s thoughts on this?

I don't know about C15th upper class dress but C16th working women wore black partlets, see Bruegel, Aertsen, Beukelaar etc paintings.In your middle picture, the lady on the right has the white chemise showing, whereas the other two ladies have the black garment covering the chemise, which suggests a possible partlet to me.

I'd say partlet, just black. if you look carefully a partlet of fine linen or silk is nearly always worn with the burgundian style gown(probably just for modesty), and its something you rarely see at reenactments. the black one would make sense when warmth was needed

Other options are that they are high necked kirtles, which should be worn under gowns, (see the train bearer in the first picture for the bloack underskirt) and the train bearer in the second picture (the closure line down the front of the black under garment - also seen in the woman behind). Garments layered for winter benefit, so a dark kirle layered under a status fabric kirtle, under a gown

They may also be over-collars (like very, very small capes - often of fur, but not always - see the illustration of Christine de Pisan and her woman planting the allegorical garden) . The distaff spinners in the first picture have button fronts, which suggests a lower status collar along the lines of a open hood's shoulder plate.